Interfaces in Java

Today's notes - Interfaces

Terminology

interface

An interface specifies behavior for a class. - Gaddis definition

It is also the keyword that defines the interface

implements

the java keyword that indicates that a class is implementing a specified interface

Notes

• interfaces provide method headers. May also provide constants. May not provide attributes (because these are not inherited).
• a class implementing an interface must implement each of the interfaces methods...this is the contract.
• interfaces provide a "multiple inheritance" mechanism. It is not inheritance, but classes that implement the same interface can be treated as if they share the "is-a" relationship.
• interfaces may be exteded. The method headers (contractual requirements) are inherited. Implementing classes must implement all methods in the child and all ancestors.

Syntax

declaration
visibility interface name

using
visibility class name implements interfaceName

Examples